Helicobacter pylori is the bacterial pathogen that causes peptic ulcers and has been linked to increased prevalence of gastrointestinal cancers. The nickel-dependent regulatory protein, HpNikR, sits at the center of the regulatory network that is vital to ability of H. pylori to both survive in the acidic environment near the gastric lumen and to thrive in the neutral pH environment near the epithelial layer of the gastric mucous membrane. The objective of this proposal is to use complementary experimental and computational techniques to determine structural and mechanistic details of the function of HpNikR. In Aim 1, the goals are the structural characterization of HpNikR at neutral pH for the apo- and nickel-bound forms, determination of three dimensional structures of HpNikR bound to a series of its DNA operons, and assessment of the oligomeric state of HpNikR in the apo- and nickel-bound forms. In Aim 2, the objectives are the examination of the nickel coordination sites in HpNikR and investigation of the role of specific amino acids in DNA-binding affinity using computational and spectroscopic methods. Elucidation of these details about HpNikR will improve understanding of the functional role of genetic regulatory pathways in H. pylori pathogenicity. PUBLIC HEALTH RELEVANCE: Infections of human gastric tissue by the pathogenic bacteria Helicobacter pylori are associated with peptic ulcers and increased prevalence of stomach and intestinal cancers. The regulatory protein HpNikR is central to the ability of H. pylori to thrive and function in the human stomach. The goal of this research is to gain insight into the structure and function of HpNikR, and the roles it plays in H. pylori virulence.